1. Field of the Invention
The present invention relates to a focus adjustment device and focus adjustment method capable of accurate focus adjustment, even when a point light source or high brightness light source are contained within a subject.
2. Description of the Related Art
If a point light source is contained within a subject, a false focus position will be detected due to the point light source, and carrying out AF (Auto Focus) with good precision is difficult. A focus adjustment device that can carry out AF with good precision even with this type of subject has therefore been proposed. For example, a focus adjustment device that sets multiple partitioned areas, counts high brightness pixels within those areas, determines an area for which that count value is a given value or more as being a point light source subject, and carries out AF in an area, among the multiple partitioned areas, in which a point light source does not exist, is proposed in Japanese patent laid open number 2013-097082 (hereafter referred to as patent publication 1). Also, in this focus adjustment device, in the event that orientation change such as pan or tilt has been detected, the process is performed again from the point light source determination.
In the determination of point light source in patent publication 1 above, without determining the size of a high brightness area there is a possibility of erroneous determination of white portions within a black subject as point light sources, and high brightness areas are searched for in pixel units involving a longer processing time. Also, with patent publication 1, although AF is carried out in an area in which a point light source does not exist, with a video there are cases where point light sources are moving, and there is a possibility that AF precision will be degraded in cases such as illuminations where it is desired to actually take a picture of a subject of point light sources. Further, with patent publication 1, in a case where pan or tilt has been detected, with AF for a movie (hereafter referred to as movie AF) etc. point light source determination is repeated with high frequency resulting in processing load being large, and being a factor in the undermining of AF stability.
A point light source subject or high brightness light source (light source subject such as a fluorescent lamp) are examples of weak subjects with which it is easy to erroneously confirm a false focus position as a focus position when carrying out contrast AF (hill climbing AF). In particular, since the subject changes sequentially in movie AF, due to camera operations such as pan and tilt, and due to movement of the subject, there is a possibility of a point light source subject and a non-point light source changing during the AF operation, and it is necessary to carry out optimum focus adjustment for either case, but the focus adjustment device of the conventional art is insufficient in this regard.